If you were to ask my friends and family how far in advance I’d prefer to schedule things, they’d probably tell you that I often say, “Let’s just play it by ear.” Meaning that when I’m not at work, I like to roll with the punches, even if a group of us have tickets for an event that is happening at a very specific time.

However, when it comes to being flexible at work, there are certain times when this approach is just unacceptable. So with that in mind, here are a few reminders of when having a loose timeline does not cut it.

1. When You Have a Hard Deadline on a Big Project

You’re probably saying, “Well, duh. I’m not going to leave a project unfinished when there’s a deadline.” However, it’s also easy to look at your deadline and start tackling the tasks that you think need to get done in the order they pop into your head. And if you’re doing so without any kind of solid action plan in place, a few problems are bound to pop up as the clock strikes midnight.

For starters, you’ll likely do tasks out of order because your head doesn’t always work in timeline fashion, and when that starts to happen, you’ll probably end up having to go back and redo what you’ve already done as you realize certain things along the way. And worse, because you’re working haphazardly, you’ll be unsure until the very end whether or not you’re doing everything needed to turn in a well-done project.

So, while it’s perfectly acceptable (and recommended) to be somewhat flexible about your typical process, a hard due date is the most glaring indicator that you shouldn’t just fly by the seat of your pants. It’s well worth sitting down, making a list of everything that needs to happen (in order), and tackling it one step at a time.

2. When You’re About to Leave for Vacation

Again, I’m not suggesting that you shouldn’t be flexible about your schedule. However, think about all the anxiety you’ve had about leaving work for an extended period in the past. You probably had a ton of emails to address before you left, a handful of projects you needed to finish up (or send status reports on), and even more meetings you needed to reschedule.

And yes, when it comes to your actual vacation, do the things that make you happy. If that’s a week of binge-watching YouTube videos of cats eating macaroni, go for it. But when it comes to getting things in order before you leave, do yourself a favor and come up with a game plan for how you’ll address everything so that you can enjoy your break.

For many people, that might mean being more organized than usual—taking a look at upcoming deadlines and either working ahead or asking the appropriate parties to push them back. It might also mean rescheduling meetings, delegating work, or asking a co-worker to fill in for you at certain points. And even though that’ll create some extra work temporarily, you’ll be in a much better position to enjoy your vacation if everything’s all set when you leave the office.

3. When You’re Continually Dropping the Ball

If you can get things done without much of a plan, more power to you. In fact, you’re probably the kind of person who makes your co-workers insanely jealous of how productive you can be without a firm to-do list in place.

But if things start falling through the cracks, take a minute to reflect on why it keeps happening. Because if you’re doing things so haphazardly and just responding to things as they come up, odds are that you’re falling behind simply because you’re disorganized. And while it might seem like the most constricting thing ever, don’t be afraid to give yourself more structure.

You can figure out where you need it by simply asking yourself these kinds of questions:

Would it help if I started using a to-do list regularly? As in every day laying out the things I need to get done—both big (finish client report) and small (check email before lunch).

Would I be more on top of big projects if I planned more meetings with my teammates leading up to the deadline?

Would I be more productive if my boss and I had regular status update meetings?

It’s never fun to structure your days, but ignoring them and continuing to drop the ball is most definitely less fun.

There are plenty of people out there who wish they could be more flexible about how they work. And if you’re the kind of person who’s willing to roll with the punches, I’m sure there have been times when that quality has come in handy. Being too rigid about the way you structure your day will eventually drive you crazy, but so will being too disorganized and reactive. So do yourself a favor and get ahead of the game sometimes, you’ll be happy you did it!